1. Field of the Invention
The present invention relates to a structure for electrically connecting external connection terminals of a circuit board to connection terminals of a cable via clips.
2. Description of the Related Art
A typical prior art board-cable connection structure has such a structure as shown in FIG. 7. Specifically, FIG. 7 shows a thermal printhead 6 which includes a circuit board 7 made of a ceramic material for example. The circuit board 7 is formed with a heating resistor 70 extending longitudinally of the circuit board 7 at a portion adjacent one longitudinal edge thereof, and a plurality of external connection terminals 71 arranged at a predetermined pitch in a row extending along the other longitudinal edge of the circuit board 7 at a longitudinally central portion thereof. A plurality of drive ICs 72 are mounted on the circuit board 7 at a widthwise central portion of the circuit board 7 at a predetermined pitch in a row extending longitudinally of the circuit board 7. The circuit board 7 is further formed with a conductor pattern for electrically dividing the heating resistor 70 into a plurality of heating elements and for individually driving the heating elements for heat generation.
The thermal printhead 6 having the above-described structure is electrically connected via a connector 8 to a harness 9 for power supply and input/output of signals. The connector 8 comprises a socket 8A connected to the circuit board 7, and a plug 8B connected to the harness 9. The electrical connection of the circuit board 7 to the harness 9 is provided by inserting the plug 8B into the socket 8A. Specifically, the socket 8A includes a plurality of clips 80 held in a housing 81. Each of the clips 80 comprises a pin portion 80a and a clamping portion 80b. The clamping portion 80b clamps the circuit board 7 together with the external connection terminal 71, so that the circuit board 7 is electrically connected to the socket 8A. The plug 8B is formed with a plurality of holes 82 for receiving the pin portions 80a of the clips 80. When the plug 8B is inserted into the socket 8A, each of the pin portions 80a is held in the corresponding hole 82 so that the harness 9 and the circuit board 7 are electrically connected.
However, since the socket 8A, the housing 81, and the plug 8B are formed of a thermoplastic resin such as nylon for example, they are likely to be adversely affected by heat and are not thermally stable. Moreover, in addition to forming the clips 80, the housing 81 and the plug 8B need to be formed, which is troublesome and increases the cost.
It is therefore an object of the present invention to provide aboard-cable connection structure which is thermally stable and which can be manufactured economically and efficiently.
Another object of the present invention is to provide a connection clip which can be advantageously used for providing such a connection structure.
In accordance with a first aspect of the present invention, there is provided an electrical connection structure which comprises a circuit board provided at an edge thereof with a plurality of external connection terminals, a flexible flat cable provided at an edge thereof with a plurality of connection terminals in corresponding relationship to the external connection terminals of the circuit board, and a corresponding number of clips. Each of the clips includes a first clamping portion open in a first direction for inserting the circuit board, and a second clamping portion open in a second direction opposite to the first direction for inserting the flexible flat cable.
In this way; the connection structure of the present invention does riot use any additional component such as a connector housing which is made of a resin material. Thus, it is possible to provide the connection structure at a lower cost while also increasing the thermal stability of the connection structure in comparison with the prior art connection structure may be adversely affected by heat due to the presence of a resin material.
Preferably, wherein each of the clips may be integrally formed by bending a metal bar. In this case, the metal bar may be a part of a leadframe.
The clip can be manufactured using conventional equipment by a conventional method such as press-working for example. Therefore, the production of the clip according to the present invention does not cost higher than prior art clips.
In a preferred embodiment of the present invention, the first clamping portion includes a first clamp leg for contact with a respective one of the external connection terminals of the circuit board, whereas the second clamping portion includes a second clamp leg for contact with a respective one of the connection terminals of the flexible flat cable. Further, the first clamping portion and the second clamping portion includes a common clamp leg arranged between and cooperating with the first clamp leg and the second clamp leg. Moreover, the common clamp leg has a first end connected to the first clamp leg, whereas the common clamp leg also has a second opposite end connected to the second clamp leg.
Preferably, the first clamp leg may have a first contact portion bulging toward the common clamp leg which has a third contact portion bulging toward the first clamp leg, whereas the second clamp leg may have a second contact portion bulging toward the common clamp leg.
Preferably, the first contact portion of the first clamp leg may be spaced, thicknesswise of the circuit board, from the third contact portion of the common clamp leg by a distance which is smaller than the thickness of the circuit board when each clip is held in a natural state.
On the other hand, the second contact portion of the second clamp leg may contact the common clamp leg when each clip is held in a natural state.
According to a second aspect of the present invention, there is provided a connection clip for electrically connecting a circuit board to a flexible flat cable. The clip comprises a first clamping portion open in a first direction for inserting the circuit board, and a second clamping portion open in a second direction opposite to the first direction for inserting the flexible flat cable.
Other features and advantages of the present invention will become clearer from the detailed description given below with reference to the accompanying drawings.